In wiper blades, the support element for the entire field swept by the wiper blade is intended to assure the most uniform possible distribution of the wiper blade contact pressure, originating in the wiper arm, against the window. By means of a suitable curvature of the unloaded support elementxe2x80x94that is, when the wiper blade is not resting on the windowxe2x80x94the ends of the wiper strip, which in wiper blade operation is pressed completely against the window, are located by the then tensed support element toward the window, even if the radii of curvature of spherically curved vehicle windows change in every wiper blade position. That is, the curvature of the wiper blade must be somewhat greater than the greatest curvature measured in the wiping field of the window to be wiped. the support element thus replaces the complicated support bracket construction with two spring rails disposed in the wiper strip of the kind used in conventional wiper blades.
In a known wiper blade of this type (German Patent Disclosure DE 26 14 457), the connection device is integrally joined to the support element. This may possibly be of secondary importance as long as the support element is made from a plastic which is therefore made by filling a suitable mold. However, if the support element is to be made of metal, then two demands directly contract one another. On the one hand, the support element should have good spring properties, but on the other the attachments of the connection device should be easily bent by approximately 90xc2x0 out of the plane of the support element and fixed in that position, so that the loads occurring in operation between the wiper blade and the wiper arm can be absorbed on stop faces of these attachments. These two demands are virtually impossible to meet unless disadvantageous compromises in the choice of material are made.
In another known wiper blade (German Patent Disclosure DE 12 47 161), the support element is provided with a connection device as a separate component. This connection device is solidly joined to the support element with the aid of rivets. The requisite bores in the support element, however, lead to an undesired, because uncontrollable, change in the support element tension, so that a satisfactory window wiping result cannot be attained.
Accordingly, it is an object of present invention to provide a wiper blade for motor vehicle windows, which is a further improvement of the existing wiper blades.
In keeping with these objects and with others which will become apparent hereinafter, one feature of present invention resides, briefly stated, in a wiper blade, in which a connection device for a driven wiper arm has a base which rests flatly on a side remote from the window of a band-shaped support element, and is connected to the band-shaped support element by a welding connection.
In the inventive wiper blade, a choice of materials that suits the demands made of the particular component can be made for both the support element and the connection device. The joining of the two components to one another is done easily and economically by means of a welded connection. Further assembly steps can be omitted. Tests have shown that a welded connection does not impair, or insignificantly impairs, the contact pressure distribution by the support element and thus the outcome of window wiping.
If the support element and the connection device of the wiper blade are of metal, it can be expedient if the welded connection is a resistance weld.
Particularly in a wiper blade in which both the support element and the connection device are made of a plastic, operationally reliable and economical fastening of the connection device to the support element can be attained by means of ultrasonic welding.
The welding itself, both in resistance welding and ultrasonic welding, can be embodied as preferably multiple spot welds.
In a wiper blade of which major demands are made in terms of the load, however, the welded connection can also be embodied by a plurality of linear welds; with a view to the specifications to be met in terms of pressure distribution, the welds may extend either crosswise to the longitudinal direction or longitudinally of the band like support element.
A connection device that can be adapted without difficulty in view of the wiper arm design is obtained if it rests flatly with the base on the side of the bandlike support element remote from the window.
Especially good lateral guidance and holding of the two components to be joined together is attained if the protrusions are embodied as strips, which extend longitudinally of the support element.
A further-improved, stable holding of the connection device to the support element is attained if on the free ends of the strips, clawlike attachments oriented counter to one another are disposed, and the spacing between the clawlike attachments and the outside, remote from the legs of the base of the U is adapted to the thickness of the support element.
For positioning the connection device on the support element in the longitudinal direction thereof, the connection device can have at least one shoulder, pointing longitudinally of the support element, with which shoulder a counterpart shoulder of the support element is associated. The result is accordingly a positive positioning aid that becomes operative before the welding operation.
Absolute securing of the mounted position of the connection device on the support element is obtained if the connection device has at least two shoulders, pointing in opposite directions, with each of which the counterpart shoulder of the support element is associated.
Expediently, the shoulders of the connection device are embodied on a protrusion of the connection device, and the counterpart shoulders and are embodied on a recess, associated with the protrusion of the support element.
Further advantages features and refinements of the invention are described in the ensuing description of embodiments shown in the drawing.